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An approach of local bond average (LBA) has been developed by extending the bond-order-length-strength correlation (Sun, C. Q. Prog. Solid State Chem.2007, 35, 1− 159) to temperature domain for the mechanism of the thermally driven bond expansion in a solid specimen. It is shown that the detectable quantities of a solid can be connected directly to the bonding identities and the response of the bonding identities to the stimulus of temperature change, being free from using the concepts in classical thermodynamics or hypothetical constants. The success of the LBA approach has been evidenced by fitting the observations from a number of specimens with derived information of atomic cohesive energy, which may go beyond the currently available approaches. [ABSTRACT FROM AUTHOR]

It has long been puzzling that water nanodroplets undergo simultaneously "supercooling" at freezing and "superheating" at melting. Recent progress (Sun et al. J. Phys. Chem. Lett.2013, 4, 2565, 3238) enables us to resolve this anomaly from the perspective of hydrogen bond (O:H-O) specific heat disparity. A superposition of the specific heat ?x(T) curves for the H-O bond (x = H) and the O:H nonbond (x = L) defines two intersecting temperatures that form the ice/quasi-solid/liquid phase boundaries. Molecular undercoordination (with fewer than four nearest neighbors in the bulk) stretches the ?H(T) curve by raising the Debye temperature TDH through H-O bond shortening and phonon stiffening. The ?H(T) stretching is coupled with the ?L(T) depressing because of the Coulomb repulsion between electron pairs on oxygen ions. The extent of dispersion varies with the size of a droplet that prefers a core-shell structure configuration?the bulk interior and the skin. Understandings may open an effective way of dealing with the thermodynamic behavior of water droplets and bubbles from the perspective of O:H-O bond cooperativity. [ABSTRACT FROM AUTHOR]